The invention relates generally to the application of fluid materials and, in particular, to devices for use in jetting fluid materials.
Jetting devices may require different types of dispensing valves, or dispensing valve components, that are dedicated to different types of dispensing applications in electronic industry applications in which minute amounts of a fluid material is applied onto a substrate. A “jetting device” is a device which ejects, or “jets”, a droplet of material from the dispenser to land on a substrate, wherein the droplet disengages from the dispenser nozzle before making contact with the substrate. Thus, in a jetting type dispenser, the droplet dispensed is “in-flight” between the dispenser and the substrate, and not in contact with either the dispenser or the substrate, for at least a part of the distance between the dispenser in the substrate. Numerous applications exist for jetting devices that dispense underfill materials, encapsulation materials, surface mount adhesives, solder pastes, conductive adhesives, and solder mask materials, fluxes, and thermal compounds. As the type of application for the jetting device changes, the type of jetting device must also adapt to match the application change.
One type of jetting device includes a needle with a tip configured to selectively engage a valve seat. During a jetting operation, the needle of the jetting device is moved relative to the valve seat by a driving mechanism. Contact between the tip of the needle and the valve seat seals off a discharge passage from a fluid chamber supplied with fluid material under pressure. Thus, to dispense droplets of the fluid material, the valve element is retracted from contact with the valve seat to allow a finite amount of the fluid material to flow through the newly formed gap and into the discharge passage. The tip of the needle is then moved rapidly toward the valve seat to close the gap, which generates pressure that accelerates the finite amount of fluid material through the discharge passage and causes a droplet of the material to be ejected, or jetted, from an outlet of the discharge passage.
Jetting devices are configured for controlled movements above the substrate and the fluid material is jetted to land on an intended application area of a substrate. By rapidly jetting the material “on the fly” (i.e., while the jetting device is in motion), the dispensed droplets may be joined to form a continuous line. Jetting devices may therefore be easily programmed to dispense a desired pattern of fluid material. This versatility has made jetting devices suitable for a wide variety of applications in the electronics industry. For example, underfill material can be applied using a jetting device to dispense fluid material proximate to one or more edges of the chip, with the material then flowing under the chip by capillary action.
In conventional jetting devices, the needle tip that contacts the valve seat is exposed to the jetted fluid material. Consequently, the needle must include various seals that provide fluid isolation of the driving mechanism for the needle from the fluid chamber in which the needle tip is located, while permitting the tip of the needle to contact the valve seat to cause fluid material jetting. Seals promote wear and friction, while the needle requires significant travel to develop enough velocity for the impact with the valve seat that generates the energy necessary for the droplet of fluid material to be jetted.
From time to time, it is necessary to clean the internal surfaces of jetting devices that are wetted with the fluid material being jetted. Because these internal surfaces are difficult to access with cleaning tools, conventional jetting devices also take a significant amount of time to clean. Disassembling and reassembling the components of conventional jetting devices is a difficult process that involves numerous tools. As a result of the complexity of jetting devices, disassembly and reassembly are lengthy procedures, even for technicians that are highly skilled.
While conventional jetting devices have proven adequate for their intended purpose, improved jetting devices are needed that address the need for less downtime in maintaining jetting devices, while introducing additional degrees of flexibility to enable the jetting devices to be relatively easily configured for a variety of jetting applications.